Niacin, also known as vitamin B.sub.3, is the common name for nicotinic acid. The physiologically active form of niacin is niacinamide, also a member of the vitamin B.sub.3 family of compounds. Niacin and niacinamide (nicotinic acid amide) function in the body as components of two coenzymes: nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP). Until recently, these vitamin B.sub.3 compounds were used exclusively to treat niacin deficiency and pellegra.
Today, however, vitamin B.sub.3 compounds have also found use in the area of skin care actives. British Patent 1,370,236 describes compositions for skin lightening containing 0.5% to 10% niacin. Similarly, U.S. Pat. No. 4,096,240 discloses the use of 0.1% to 10% niacinamide for skin lightening. Vitamin B.sub.3 compounds have also been found useful in regulating the texture of human skin. See PCT application WO 97/39733, to Oblong et al.
However, when topically applied to the skin, only about 2-4% of the applied vitamin B.sub.3 compound actually penetrates into the skin. Thus, there exists a need for cosmetic compositions comprising vitamin B.sub.3 compounds which provide improved skin penetration of vitamin B.sub.3 compounds. The present inventors have discovered that cosmetic compositions which incorporate vitamin B.sub.3 compounds in a polar solvent such that the vitamin B.sub.3 compound exceeds the saturation solubility of the polar solvent improves the overall skin penetration of the vitamin B.sub.3 compound.
It is, therefore, an aspect of the present invention to provide cosmetic compositions comprising a polar solvent and vitamin B.sub.3 compounds as undissolved crystals.
A further aspect of the present invention is to provide lipstick compositions comprising a polar solvent and vitamin B.sub.3 compounds as undissolved crystals.
These and other aspects will become readily apparent from the detailed description which follows.